The characteristics of airborne transmission and thermal comfort with the micro-environment systems and perforated duct system

One of the major challenges in modern buildings is to guarantee healthy indoor air quality and excellent thermal comfort in an energy efficient manner. This paper focused on two micro-environment ventilation systems, namely the personalized ventilation combined with radiant panel system (PVRP) and the local low velocity unit combined with radiant panel system (LVRP) and studied the potentials of minimizing the airborne infection risk and thermal comfort. The performance was compared with a typical mixing ventilation system, where supply air is released from a perforate duct. The droplet nuclei of an infected person are simulated with tracer gas (SF6) released by a thermal breathing manikin. The results show that the inhaled concentration of the exposed person was much lower than at the other locations with two micro-environment systems. The average contaminant removal efficiency was 1.6, 1.3 and 1.0 with the PVRP, LVRP and perforated duct systems, respectively. With the PVRP and LVRP systems, due to the local airflow rates from personalized ventilation and low velocity unit, and the cooling load from panels, the air temperature near the manikin is lower than the exhaust temperature. When the heat gain increased, the drift risk with two micro-environment is still under 10%. With the perforated duct system, the drift risk is increased with the increasing heat gain.